Preformed strip and method for splicing conveyor belts

ABSTRACT

A preformed strip ( 20 ) of unvulcanized rubber having a plurality of strand receiving grooves ( 22 ) for splicing the ends ( 11, 12 ) of steel cord or strand reinforced rubber conveyor belts ( 10 ) is disclosed along with a method of forming the spliced joint.

TECHNICAL FIELD

[0001] This invention relates to a method and apparatus for formingsplices at the ends of conveyor belts.

BACKGROUND OF THE INVENTION

[0002] Conveyor belts are commonly used as a means to move material fromone location to another. In large mining operations, the conveyor beltis generally formed of a rubber body embedded with steel cords orstrands. A cover compound can be used at the surface wherein thematerial is to be conveyed. Generally the compound is very abrasion andcut resistant and of sufficient thickness to prevent the rocks beingconveyed from tearing the belt. A pulley compound can be used on theinterior surface, this rubber is ideally suited for improved wear as thebelt traverses over the pulleys used to drive the belt.

[0003] These steel corded or stranded belts may extend several miles andcost millions of dollars to install and fabricate. The fabrication ofsuch belts occurs initially at a factory wherein steel strands or cordsare arranged in a coplanar relationship parallel to the surface of thebelt so that the belt will exhibit uniform expansion and minimizeweaving as it traverses which can cause belt damage.

[0004] The prior art method of fabricating belts requires the steps ofvulcanizing the rubber belt and winding it onto large spools forshipping to the site. Once the spools of belt are received at the site,the ends must be prepared for splicing by removing the vulcanized rubberfrom the strands over a distance determined to be sufficient to provideenough joint length to make a secure splice.

[0005] Removal of the rubber can be a very time consuming and tedioustask. Often times piano wire is used to peel the vulcanized rubber fromthe strands. In large belts of several feet in width over a hundredstrands must be exposed at each joint end. Once exposed, the strands hadto be cleaned of as much of the vulcanized rubber as possible. Thestrands were then cleaned with solvents such as toluene and then abonding agent was applied comprising a 3:2 mixed solution of “ChemlokNo. 203” and xylene, for example, and rubber cement is applied to thestrands and dried. After the preparation of both ends as described inU.S. Pat. No. 3,487,871 entitled “A METHOD OF JOINING CONVEYOR BELTSHAVING STEEL CORDS EMBEDDED THEREIN” granted Jan. 6, 1970, a joiningmember is formed made of vulcanized or semi-vulcanized rubber of thesame quality as the rubber used in the formation of the belt. The upperface of the member is preferably made of a non-vulcanized rubber andprovided with a plurality of strand receiving grooves. Once the strandsare in place, a bonding agent of the type described above is preferablycoated on the faces of the surfaces to insure complete bonding. Whilethis prior ant patent use the term “non-vulcanized rubber” beingpreferable at the melting surfaces of the otherwise vulcanized orsemi-vulcanized member (13), it is believed that the term means “havingat least its upper surface formed of incompletely vulcanized rubber” aswas required in the claim of the patent. An important limitation whenthe member for splicing is semi-vulcanized at this grooved surface, theuse of semi-cured rubber forced the use of bonding solvents. Thesesolvents are high in VOC's and the liberal use of xylene and toluenecreates carcinogenic risks to the personnel. In developed parts of theworld, the use of such solvents is greatly discouraged.

[0006] A second limitation of the prior art splicing member is that themember was apparently molded to the exact width of the belt and hadexactly twice the number of strands as the belt. This meant that foreach belt width, there had to be a unique member since conveyor beltsare not standardized in width or in the size or in the number of strandsto use the concept taught in that patent required specially designedmolds.

[0007] A third limitation of the method of splicing described in U.S.Pat. No. 3,487,871 was that the strands had to be free of any of thevulcanized belt rubber which, if left on the strands, adversely affectedthe bonding.

[0008] An object of the present invention is to eliminate the need tosemi-vulcanize the splicing member.

[0009] Another objective is to make the use of solvents unnecessary.

[0010] Still another objective is to eliminate the need to completelystrip the strands of all vulcanized rubber prior to splicing.

[0011] A still further objective is to provide a splicing strip that canbe used in multiples independent of the width of the belt or thecorresponding number of strands.

[0012] A still further objective is to improve the splice strength whilesaving time in splice preparation.

SUMMARY OF THE INVENTION

[0013] A method of splicing the ends (11, 12) of conveyor belts (10)having vulcanized rubber (2) with steel strands (1) embedded in thevulcanized rubber is disclosed. The method has the steps of (a) removinga portion of the rubber (2) from the belt ends (11, 12) to be joinedexposing a plurality of strands (1); (b) providing at least twounvulcanized strips (20) of rubber, at least one strip (20) being abottom strip having a plurality of substantially parallel strandreceiving grooves (22) located on an upper surface (24), the other atleast one strip being a top strip (20); (c) placing exposed strands (1)of the belt ends (11, 12) being joined in the grooves (22) of the bottomstrip (20); (d) placing the top strip (20) overlying the bottom strip(20) and vulcanizing the strips (20) together thereby forming thespliced joint.

[0014] In a preferred method, the step of removing the vulcanized rubber(2) exposing a plurality of strands (1) includes leaving the strands (1)at least partially sheathed in the vulcanized rubber, most preferably ina coating of the vulcanized rubber (5) whereby the step of vulcanizingthe strips (20) together includes vulcanizing the strip (20) to the atleast partially sheathed strands (1).

[0015] The step of providing at least two unvulcanized strips (20) ofrubber includes the steps of providing at least two bottom strips (20)and positioning the strips (20) adjacently to increase the width of thestrips (20), and cutting one of the at least two bottom strips (20)parallel to the grooves (22) thereby substantially matching the totalstrips width (W_(S)) to the conveyor belt width (W_(B)).

[0016] The top strips (20) may be similarly grooved as the bottom strips(20). Preferably, the top and bottom strips are the same incross-sectional profile.

[0017] The step of providing the top or bottom strips (20) includes thesteps of calendering the strip (20), the calender having a roller (352)having a plurality of parallel component forming ridges (356), theridges (356) forming the strand receiving grooves (22) of the uppersurface (24).

[0018] In one embodiment, the step of calendering includes the step ofapplying the bottom strip (20) onto a strip of pulley contacting rubbercompound (3) as the bottom strip is being formed at the calender rollerassembly (200) thereby forming a dual compound bottom strip (20). Thetop strip (20) can similarly be made a dual compound by applying it to atop cover rubber compound (4).

[0019] Each of the above methods of splicing uses an elastomeric strip(20) for splicing steel cable reinforced belts (10), the strips (20)having a width W_(S) and length L_(S). The strips (20) are characterizedby an uncured strip (20) having a cross-sectional profile extendingacross the width W_(S) of the strip (20). The profile having a pluralityof substantially semi-circular depressions extending parallel along thelength of the strip. Each depression providing a steel cable receivinggroove (22) for placement of a steel cable or strand (1).

[0020] It is preferred that strips (20) has a width (W_(S)) less thanthe width (W_(B)) of the belts (10) to be spliced thereby requiring aplurality of strips (20) for each splice joint.

[0021] Most preferably, the strips are prepackaged in kits of four ormore strips (20) for each splice joint.

BRIEF DESCRIPTION OF DRAWINGS

[0022]FIG. 1 is a fragmentary cross-sectional view of an exemplary beltstructure having steel strands embedded in vulcanized rubber.

[0023]FIG. 2 is a perspective view of a belt end prepared for attachmentto a corresponding belt end and a plurality of the preformedunvulcanized strips of rubber for joint splicing.

[0024]FIG. 3 is a steel cord strand shown sheathed in a coating of thevulcanized belt rubber.

[0025]FIG. 4 is a side elevation view of a vulcanizing press for forminga belt joint in accordance to the invention.

[0026]FIG. 5 is a perspective view of a calender apparatus for formingthe preformed elastomeric strip.

[0027]FIG. 6 is a cross-sectional view of the calender roller withridges for forming the strand receiving grooves in the strip.

[0028]FIG. 7 is a cross-sectional view of a preferred strip.

[0029]FIG. 8 is a cross-sectional view of a preformed strip with a layerof bottom pulley rubber laminated to the strip.

[0030]FIG. 9 is a cross-sectional view of a preformed strip with a layerof top cover rubber laminated to it.

[0031]FIG. 10 is a perspective view of the strip assembly in anexemplary kit for splicing a joint for a belt reinforced with steelstrands embedded in rubber.

DETAILED DESCRIPTION OF THE INVENTION

[0032] With reference to FIG. 1, an exemplary conveyor belt (10) will beobserved. The belt (10) has a plurality of steel cords or strands (1)embedded in a core or central layer of rubber (20). As illustrated, thecentral layer (2) is bounded by a bottom layer of rubber (3) of acompound ideally suited for contacting the drive pulleys of the conveyorsystem (not shown) and a cover layer (4) of a rubber compound ideallysuited for abrasion and cut resistance. Additionally, such belts (10)may include additional textile or fabric layers or alternatively areformed utilizing only a single homogeneous rubber without a top orbottom compound while the steel strands of the belt may be impregnatedor coated with a thin rubber bonding layer or sheath (5) to enhance cordadhesion. Nevertheless, the present invention is ideally suite tofacilitate the splicing of almost any known type of rubber conveyorbelts (10) having steel cords or strands (1).

[0033] As shown, preparation of the belt ends (11, 12) to be joined isillustrated in FIG. 2. The belt ends (11, 12) has a portion of the body(14) of the belt (10) removed to expose the steel strands (1). Forconvenience, the term “body (14) of the belt (10)” is intended toinclude all body elements such as the central layer (2), the bottom (3),the cover (4), and any other layers. That portion of the body (14) isremoved preferably across the width of the belt in a diagonallyextending on. This insures that the splice seam will not approach adrive pulley simultaneously. Additionally the layer of rubber on the topsurface of the strands may be cut back further than the lower layer ofrubber below the strands, this method of ends (11, 12) preparation iscommonly referred to as a stepped contour. These features, although notrequired, can improve the splice joint in some applications.

[0034] Once the rubber body (14) is removed from an end (11, 12), thestrands (1) of steel cord are exposed. In some techniques of removingthe rubber body (14) steel piano wire is used to peel the rubber off thecords (1). In that method of body removal (14), virtually all of therubber sheathing the steel cord is removed such that the cords are onlyat least partially sheathed in cured rubber. If desired, the remainingrubber bonded to the cords or strands can be removed by wire brushes orthe like. This technique is quite tedious and time-consuming, however,and is preferably avoided.

[0035] An alternative method of removing the rubber body (14) includesusing a means having contoured cutting surfaces that remove the rubberbody (14) while leaving the strands (1) coated in a thin sheath ofrubber (5) as shown in FIG. 3. In this technique, the strands (1) can bebuffed to enhance the adhesion of the cured rubber sheath (5) prior tosplicing the joint.

[0036] It is important to note that the present invention is ideallysubmitted to be used on belts; wherein the strands are exposed at theend of the belts as a result of a technique of manufacture. In such acase, the step of preparing the ends (11, 12) for splicing can beavoided or modified eliminating the step of removing the cured rubber.

[0037] As shown in FIG. 2, the exposed strands (1) are ideally placed indepressions in preformed strips (20) of unvulcanized rubber. Thesedepressions each represent a strand receiving groove (22). Ideally, thenumber of grooves (22) per inch are twice the number of strands per inchat one end of the belt.

[0038] Each preformed strip (20) of rubber splicing has a width (W_(S))and a length L_(S) as shown in FIG. 2. The strips (20) has a firstsurface (24) having a plurality of grooves (22) and a second surface(26), the second surface (26) being generally flat or planar.

[0039] By orienting the flat strip (20) with the grooved first surface(24) adjacent the strands (1), the strands (1) of one end (11) can beplaced in every other groove (22) while the strands (1) of the other end(12) fills the grooves (22) remaining to be filled. The resultingstrands (1) from end (11) and those from end (12) form an overlappingarray of strands (1).

[0040] Since the number of strands (1) in the splice joints areapproximately double the number of strands in the rest of the conveyorbelt (10), it is possible to vary the length of the cords or strands (1)in a number of patterned sequences. The principle concept being that acord (1) cut short in end (11) would be adjacent one or two long cords(1) in end (12) and vice-versa. The resultant effect is that the cords'ends do not bend around the drive pulley at a simultaneous occurrencegiving rise to a peak stress. While these splicing techniques are wellknown in the art, it is important to note that they are easily adaptableto the present invention.

[0041] Once the cords or strands (1) are all placed in the grooves (22)in a proper splicing sequence, a top strip or strips is placed over thesplice opening covering the strands with a strip of uncured rubber onboth the top and bottom.

[0042] Preferably, the top strip may be grooved similar to the bottomstrip. Most preferably, the top and bottom strips are the same inprofile and composition.

[0043] Alternatively, the top strip may simply be a flat component ofuncured rubber.

[0044] Dependent on the amount of opening needed for the splice joint,the strips (20) may be provided slightly larger than needed in such acase, the strips may be trimmed to fit as needed.

[0045] Most preferably, the strips are sized in terms of length toprovide the optimal splicing length L_(S) for strength and durabilityand no trimming or cutting of the strip would be recommended. In thiscase, the belt manufacture can at least insure the splice length issufficient.

[0046] In terms of strip width (W_(S)) an important feature of thesplicing strip is that they are preformed to a width (W_(S)) that isgenerally narrower than the belt width (W_(B)). In belts having a widthof five feet or more, it can easily be appreciated that pluralities ofnarrower strips are easier to handle. The splicing operator simply canplace as many strips as are needed to cover the strands and then musttrim cut the last strip to substantially match the overall belt width.Ideally, this trimming simply requires taking a hot knife or similarcutting element and passing it through a groove (22) of the strip. Thisprocedure is applicable to both the top and the bottom of the splicejoint.

[0047] Once the uncured strips (20) are positioned and the strandsproperly placed in the grooves (22), the joint area is placed in acuring press (30) as is shown in FIG. 4. Once cured, the splice iscomplete. The advantages of precision and quality control improvementscan be easily appreciated over the more arcane techniques used in theprior art but, in addition to making a superior splice, this method canreduce splicing time by as much as half over current techniques. Whenone considers that as many as a hundred splices may be needed in a largemining belt, a reduction from 8 hours to less than 4 hours to complete asingle splice joint has obvious cost and time savings.

[0048] In FIG. 5, a calender apparatus (100) is shown for forming thepreformed elastomeric strip (20). The apparatus (100) has one or morecalender assemblies (200), each assembly (200) has a pair of calenderrollers (350, 352).

[0049] In FIG. 6, one of the rollers (352) has a plurality of ridges(356) oriented in a parallel arrangement, the ridges (356) form theplurality of depressions (22) in the cross-sectional profile of thestrips (20), these groove forming ridges (356) form the strand receivinggrooves (22). One of the calender rollers (352), preferably the one withthe ridges (356) has a component forming depression (354) whichestablishes the overall profile of the strip (20). The strip (20) itselfis formed by delivering the uncured rubber (40) to the nip of thecalendered rollers. As shown the means (360) for delivering the rolleris an extruder (360) that processes the rubber into a round strand (40)that is fed into the nip. As the strip profile is formed, the strip (20)is transferred directly onto a conveying means (600). As shown, in theconveying means can be a steel conveyer belt (207).

[0050] Alternatively, the strip (20) can be transferred onto anotherlayer of rubber (3, 4). As shown in FIGS. 8 and 9 respectively, thepreformed strips can be laminated onto a layer of bottom pulley rubber(3) or onto a layer of top cover rubber (4), thus, making specific topstrips (20) and bottom strips (20). In such a case, two calenderassemblies can be used to simultaneously form the two layers as shown inFIG. 5.

[0051] It is believed preferable to transfer the strip (20) onto acarrier member such as liner (50). Most preferably a semi-rigid polyliner (50).

[0052] As shown in FIG. 10, the strip (20) when placed on a liner (50)can be coiled and stacked vertically. Assuming the strip (20) isattached or transferred onto the liner (50) at the location where it isformed, i.e. at the calender roller, then the adhesion to the liner (50)is such that the strip (20) will be securely fixed to the liner (50).This minimized the potential for shipping and handling damage. As shown,the number of coils sent in a kit should be equal to the amount neededto make a splice joint.

[0053] As illustrated, the above apparatus (100) for making the strips(20) may include additional calender assemblies (200) to form either thetop cover layer (4) or a bottom pulley layer (3). Nevertheless, theprinciples of forming strips (20) advantageously enables the componentto be preformed in a green or uncured state. This insures that thestrips (20) can be used without the necessity of using solvents andcements.

[0054] While certain representative embodiments and details have beenshown for the purpose of illustrating the invention, it will be apparentto those skilled in this art that various changes and modifications maybe made therein without departing from the spirit or scope of theinvention.

1. The method of splicing the ends (11, 12) of conveyor belts (10)having vulcanized rubber (12) with steel strands (1) embedded in thevulcanized rubber comprising the steps of: exposing a plurality ofstrands (1); providing at least two unvulcanized strips (20) of rubber,at least one strip (20) being a bottom strip having a plurality ofsubstantially parallel stand receiving grooves (22) located on an uppersurface (24), the other the at least one strip (20) being a top strip;placing the exposed strands (1) of the belt ends (11, 12) being joinedin the grooves (22) of the at least one bottom strip (20); placing thetop strip (20) overlying the bottom strip (20) and vulcanizing thestrips (20) together and to strands (1) thereby forming the splicedjoint.
 2. The method of splicing the ends (11, 12) of a conveyor belt(10) of claim 1 wherein the steps of providing exposing a plurality ofstrands includes removing a portion of the belt ends to be joined, atleast two unvulcanized strips of rubber included the steps of providingat least two bottom strips and positioning the strips adjacently toincrease the width of the strips, and cutting one of the at least twobottom strips parallel to the grooves, thereby, substantially matchingthe total strips width to the conveyor belt width.
 3. The method ofsplicing the ends (11, 12) of a conveyor belt (10) of claim 1 whereinthe top strips (20) are similarly grooved (22) as the bottom strips(20).
 4. The method of splicing the ends (11, 12) of a conveyor belt(10) of claim 2 wherein the top strip (20) is similarly grooved as thebottom strip (20).
 5. The method of splicing the ends (11, 12) of aconveyor belt (10) wherein the top and bottom strips (20) are the same.6. The method of splicing the ends (11, 12) of a conveyor belt (10) ofclaim 1 wherein the step of providing that the top or bottom strips (20)includes the steps of calendering in strips (20), the calenders (350,352) having a plurality of parallel component forming ridges (356), theridges (356) forming the strand receiving grooves (22) of the uppersurface (24).
 7. The method of splicing the ends (11, 12) a conveyorbelt (10) of claim 1 wherein the step of calendering includes the stepof applying the bottom strip (20) onto a strip of pulley contactingrubber compounds as the bottom strip (20) is being formed at thecalender roller thereby forming a dual compound bottom strip (20). 8.The method of splicing the ends (11, 12) a conveyor belt (10) of claim 6wherein the step of calendering includes the step of applying the topstrip (20) onto a strip of top cover rubber compound (4).
 9. The methodof splicing the ends (11, 12) of conveyor belts (10) of claim 6 whereinthe bottom or top strips are applied to a separation liner (50) as theyare being formed.
 10. The method of splicing the ends (11, 12) aconveyor belt (10) of claim 1 wherein the number of strands receivinggrooves (22) is about twice the number of strands (1) from an end (11,12) of the belt (10).
 11. Elastomeric strips (20) for splicing a steelcable reinforced belt (10), the strip (20) having a width (W_(S)) and alength L, each strip (20) characterized by an uncured strip having across-sectional profile extending across the width (W_(S)) of the strip,the profile having a plurality of substantially semi-circulardepressions extending parallel along the length of the strip, eachdepression providing a steel strand receiving groove (22) for placementof a steel strand (1).
 12. The elastomeric strip (20) for splicing asteel cable reinforced belt (10) of claim 11 further characterized inthat the width (W_(S)) of one strip (20) is less than the width (W_(S))of the belts (10) to be spliced, thereby, requiring a plurality ofstrips (20) for each splice joint.
 13. The elastomeric strip (20) forsplicing a steel cable reinforced belt (10) of claim 11 wherein a topstrip (20) further has a cover layer elastomer (4) laminated to a side(26) of the strip (20) opposite the depressions.
 14. The elastomericstrip (20) for splicing a steel cable reinforced belt (10) of claim 11wherein a bottom strip further has a pulley layer (4) elastomerlaminated to a side (26) of the strip (20) opposite the depression. 15.A splice joint kit of the elastomeric strips (20) for splicing a steelcable reinforced belt (10) of claim 1, the kit characterized by four ormore uncured strips (20), each strip (20) being placed in an elongatedshipping container and spaced by a separator means.
 16. The kit of claim14 wherein the separator means (50) is a separation liner (50).